feat: update default electricity unit rate

Rate changed to 26.35p with effect from 1st October 2025

Author: stringiest

config/application.rb

@@ -77,6 +77,6 @@ class Application < Rails::Application
 
     config.session_store :disabled
 
-    config.x.default_unit_rate = 25.73
+    config.x.default_unit_rate = 26.35
   end
 end